BART fares will be going up in July as part of the transit agency's policy of regularly scheduled increases, but officials are pondering who should pay the higher fares, how much more they should be charged, and whether the automatic increases should be continued.

BART has raised fares every other year since 2006 to keep pace with inflation, and to remove some of the politics from the fare-setting process. A policy adopted in 2003 called for an automatic increase based on the state and national inflation rates minus 0.5 percent and rounded to the nearest nickel. The increases were to be applied every other January starting in 2006 and ending in 2012. BART directors voted in 2010 to use a budget surplus to delay this year's increase by six months.

With the fare increase looming, BART officials are looking at tweaking the formula. Three options - each of which would raise about $5 million - are being considered:

-- Sticking with the inflation-based increase, which would add 1.4 percent - from no increase to 15 cents - to the cost of every ride.

-- Raising the cost of only transbay rides by 10 cents.

-- Increasing the cost of each trip by a nickel.

An article posted on BART's website Friday tied the increase to the transit agency's efforts to raise money to replace its fleet of 669 rail cars, most of which are nearly 40 years old. BART needs to come up with $750 million of the expected $3 billion cost.

BART directors also need to decide whether to extend the inflation-based fare increases in even-numbered years through 2020. According to estimates, fares would be expected to increase about 3.9 percent each of those years.

Depending on which option the BART board chooses for the July increase, some riders could have to pay more while others would be spared. And while the amounts are small, the plans will likely spark discussion about equity.

If BART stays with the inflation-based increases, fares for short trips such as those within San Francisco or downtown Oakland, would remain unchanged. The priciest ride - from Pittsburg/Bay Point to San Francisco International Airport - would increase by 15 cents. A trip from Walnut Creek to San Francisco would rise from $4.75 to $4.85, while a ride from Hayward to Berkeley would go from $3.25 to $3.30.

The proposal to raise fares a dime for trips through the Transbay Tube would mean no fare increases for riders remaining in the East Bay, traveling within San Francisco or up and down the Peninsula. Raising fares a nickel for every ride would spread the pain systemwide but would mean that some taking the roughly 57-mile ride from Pittsburg/Bay Point to Millbrae - BART's longest - would be hit with the same increase as someone traveling three blocks from Embarcadero to Montgomery.

Under all of the proposals, discounts for youth, seniors and the disabled would continue to be 62.5 percent of the regular fares, rounded to the nearest nickel.

BART will hold five community meetings to seek comments on the July and future fare increases, as well as Clipper card distribution for youth and seniors and a draft environmental justice policy. The meeting schedule, fare charts and more information are available at links.sfgate.com/ZLHO.